Abstract
The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2]rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylenebridged bipyridinium (P-BIPY2+) unit and a cyclobis (paraquatp-phenylene) (CBPQT4+) ring component. The [2]rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT4+ring encircles the DNP unit. Reduction of the CBPQT 4+ leads to the CBPQT2(•+) diradical dication while the P-BIPY2+ unit is reduced to its P-BIPY•+ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT2(•+) ring along the dumbbell to surround the P-BIPY •+ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY•+ unit, a property which is absent between these redox centers in the free dumbbell and in the 1:1 complex formed between the CBPQT2(•+)ring and the radical cation of methyl-phenylene-viologen (MPV•+). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (kET =1.33 × 107 s-1) and activation energy (ΔG‡ = 1.01 kcal mol-1) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus-Hush theory.
| Original language | English |
|---|---|
| Pages (from-to) | 11546-11551 |
| Number of pages | 6 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 109 |
| Issue number | 29 |
| DOIs | |
| Publication status | Published - Jul 17 2012 |
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Cite this
Mechanically induced intramolecular electron transfer in a mixed-valence molecular shuttle. / Barnes, Jonathan C.; Fahrenbach, Albert C.; Dyar, Scott M.; Frasconi, Marco; Giesener, Marc A.; Zhu, Zhixue; Liu, Zhichang; Hartlieb, Karel J.; Carmieli, Ranaan; Wasielewski, Michael R; Stoddart, J. Fraser.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 109, No. 29, 17.07.2012, p. 11546-11551.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Mechanically induced intramolecular electron transfer in a mixed-valence molecular shuttle
AU - Barnes, Jonathan C.
AU - Fahrenbach, Albert C.
AU - Dyar, Scott M.
AU - Frasconi, Marco
AU - Giesener, Marc A.
AU - Zhu, Zhixue
AU - Liu, Zhichang
AU - Hartlieb, Karel J.
AU - Carmieli, Ranaan
AU - Wasielewski, Michael R
AU - Stoddart, J. Fraser
PY - 2012/7/17
Y1 - 2012/7/17
N2 - The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2]rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylenebridged bipyridinium (P-BIPY2+) unit and a cyclobis (paraquatp-phenylene) (CBPQT4+) ring component. The [2]rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT4+ring encircles the DNP unit. Reduction of the CBPQT 4+ leads to the CBPQT2(•+) diradical dication while the P-BIPY2+ unit is reduced to its P-BIPY•+ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT2(•+) ring along the dumbbell to surround the P-BIPY •+ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY•+ unit, a property which is absent between these redox centers in the free dumbbell and in the 1:1 complex formed between the CBPQT2(•+)ring and the radical cation of methyl-phenylene-viologen (MPV•+). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (kET =1.33 × 107 s-1) and activation energy (ΔG‡ = 1.01 kcal mol-1) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus-Hush theory.
AB - The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2]rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylenebridged bipyridinium (P-BIPY2+) unit and a cyclobis (paraquatp-phenylene) (CBPQT4+) ring component. The [2]rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT4+ring encircles the DNP unit. Reduction of the CBPQT 4+ leads to the CBPQT2(•+) diradical dication while the P-BIPY2+ unit is reduced to its P-BIPY•+ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT2(•+) ring along the dumbbell to surround the P-BIPY •+ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY•+ unit, a property which is absent between these redox centers in the free dumbbell and in the 1:1 complex formed between the CBPQT2(•+)ring and the radical cation of methyl-phenylene-viologen (MPV•+). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (kET =1.33 × 107 s-1) and activation energy (ΔG‡ = 1.01 kcal mol-1) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus-Hush theory.
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U2 - 10.1073/pnas.1201561109
DO - 10.1073/pnas.1201561109
M3 - Article
VL - 109
SP - 11546
EP - 11551
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 29
ER -